NEW CONCEPTIONS IN SCIENCE 



ether -waves. This series covers the first faint 

 tremblings sent out, let us say, by a bar of iron that 

 we have begun to raise in temperature, up through 

 the red glow which first makes the bar visible in the 

 dark, to the dazzling light it sends forth when it has 

 become white-hot. What we call light and heat, 

 then, are but purely personal, or subjective, sensa- 

 tions, aroused by the same medium, and differing 

 only in the rapidity of motion in this medium. 



Have we reached nature's limits, or may we 

 farther go? At the moment exploration of the 

 ultra-violet seems blocked, but at the opposite end 

 subtle experiment is reaching out to link yet an- 

 other great field of science to this long chain. That 

 is the field one might almost say empire of elec- 

 tricity. I have elsewhere 1 given account of re- 

 cent endeavors to ascribe electrical phenomena to 

 the movement of extremely minute particles of 

 matter, a thousandfold smaller than the smallest 

 atom known, called corpuscles, or electrons. How- 

 ever this may turn out, it is certain that some forms 

 of electricity and heat and light are very close of 

 kin, apparently merely varieties of ether-motion. 



This identity was predicted by Clerk-Maxwell in 

 a purely mathematical calculation more than forty 

 years ago, long before any experimental evidence 



1 See " Progress towards an Explanation of Electricity, "p. 131. 



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